Method for producing polyols and polyols

ABSTRACT

The present invention provides an improved process for producing polyols from polyurethane wastes. The polyols produced by that process are further used to generate polyurethanes. According to the present invention polyurethane wastes are added to a mixture of at least one diol and at least one secondary alkyl amine and reacted at temperatures in the range of 120 to 220° to produce a mixture of polyether alcohols with a dissolved or dispersed mixture of substituted ureas.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/EP99/02558 which has an Internationalfiling date of Apr. 15, 1999, which designated the United States ofAmerica.

This invention relates to a process to produce polyols and to polyols asdefined in claim 1.

BACKGROUND OF THE INVENTION

It is well known in the art to dissolve polyurethane foams in lowmolecular weight glycols and thus to produce polyols for the productionof polyurethane rigid foams. It is further known to cleave the urethanegroup by strongly basic aliphatic amines to react them into substitutedurea groups.

In U.S. Pat. No. 4,162,995 e.g. the simultaneous glycolysis andammonolysis of polyurethanes by glycols, polyols, ammonia or ammoniumhydroxide to form a mixture of polyols is described in which theresultant amines are either separated or further processed. According tothis invention a second step in the procedure and only the use ofammonia is allowed. In U.S. Pat. No. 3,404,103 a process is describedfor the simultaneous alcoholysis and ammonolysis with pressure in thepresence of methanol and ammonia at elevated temperature to produce amixture of polyols and amines and ureas, resp., which are separatedafter cleavage of the macromolecules. To accelerate the ammonolysisstrongly basic catalysts are further added to the reaction mixture. Inthis process a pressure step and the work-up (separation of methanol,catalysts and excess ammonia)of the polyols are necessary before furtherprocessing. The catalysis by tertiary amines of the glycolysis isdescribed e. g. in DE-PS 27 38 572. According to U.S. Pat. No. 3,708,440dialkanol amines and aliphatic diols are used together to solvolysepolyurethane rigid foams and polyisocyanurate foams at elevatedtemperatures. U.S. Pat. No. 4,110,266 relates to the reaction ofpolyurethane rigid foams or polyisocyanurate foams with alkanolamines,the separation of any excess of them and the use of the reaction mixtureas starter of polyols. U.S. Pat. No. 3,117,940 is directed to theexclusive use of primary aliphatic amines for the aminolysis ofpolyurethane waste.

In the processes described in said patents it is disadvantageouslyattempted to enhance the comparably low basicity of the alcohols, aminoalcohols and ammonia, resp., by adding further catalysts to result inuseful reaction times for cleaving polyurethanes.

Object of the present invention is to provide an improved process toproduce polyols from polyurethane wastes as well as polyols according tothis process to produce polyurethanes from them.

According to the present invention polyurethane wastes are introducedinto a mixture of at least one diol and at least one secondary alkylamine and reacted at temperatures in the range of 120 to 220° C. bywhich process a mixture of polyether alcohols and substituted polyureasdissolved or dispersed in them is formed.

The ratio of diol and amine depends on several parameters among whichthe average molecular mass of the reactants and the type of polyurethaneare most essential. It should be kept in mind that the secondary alkylamine is both catalyst of the depolymerization reaction and reactant andhence must not be used in excess. If related to the diol andpolyurethane present the amine used may be varied in a broad range ofmass ratios which range about to 100:100:50 as a lower limit and100:25:5 as an upper limit for the ratio of polyurethane:diol:amine.Advantageously, a range of 100:50:25 to 100:25:6 is used. Depending onthe type of polyurethane, the reaction product nearly does not containfree amine making further work-up not neccessary.

Surprisingly it was found that polyurethane wastes, especiallypolyurethane foam wastes, dissolve comparably rapidly in mixtures of adiol and a secondary alkyl amine and lead to polyol mixtures so farsuitable ratios of reactants are used. The polyol mixtures can be usedto produce semi-rigid foams, rigid foams, coatings, or adhesives.

The polyols of the invention are favorably produced by reactingpolyurethane soft foams by their successive introduction into a mixtureof a lower poly(alkylene glycol) and a secondary alkyl amine at atemperature ranging from 120° C. to 220° C. Alternatively, the processof the invention may be carried out by gradually reacting polyurethanerigid foams in a mixture consisting of a lower poly(alkylene glycol) anda secondary alkyl amine at temperatures in the range of 120 to 220° C.

A further embodiment of the present invention relates to the reaction ofelastic polyurethanes or microcellular elastic polyurethanes in amixture of a diol and at least one secondary alkyl amine at temperaturesin the range of 120 to 220° C. where the mixture of diol and amine is inthe mass range of 1:2 to 1:9 and this mixture is in the ratio to theelastomeric polyurethane in a weight ratio up to 1:9.

Especially favored is a process according to the invention by whichpolyurethanes are reacted with a mixture of poly(alkylene glycol) ofaverage molecular mass from 108 to 600 and a di-n-alkylamine with achain length of the alkyl groups of 2 to 6 in a temperature range of 130to 200° C. Poly(alkylene glycol) fractions having an average molecularmass of 200, 300, 400, or 600 are preferred since these fractions showto be good solvents for the foams and the substitued ureas derived fromthe urethane groups and further act as cell opening agents duringfoaming and improve foam quality when used in the concentrationaccording to the invention.

This invention shows several advantages.

The combination of glycolysis and aminolysis in the recycling ofpolyurethanes leads to a completely different reaction mechanism of thedepolymerization of the polyurethanes compared to the state of the artglycolysis. During glycolysis the cleavage proceeds preferably bytransesterifaction at the urethane groups and as secondary reactionswith a nucleophilic cleavage of the polyureas and a decarboxylation ofthe urethane groups, both with the formation of primary aromatic amines.Contrary to this, by cleaving the polyurethanes by a combination ofglycolic hydroxyl groups and secondary amino groups the urethane groupsare transformed to trisubstituted urea groups and because of the basicreaction conditions a nucleophilic reaction at the urea groups of thepolyureas takes place in the trace range. During the reaction of thecombination of glycol and secondary alkyl amine with the polyurethane,hence, are produced mainly the long chain polyether alcohols from thepolyurethanes and the polyureas from the isocyanate and the secondaryalkyl amine, i.e. no free primary aromatic amines. The polyureas arepresent in the mixture of lower molecular weight glycol and long chainpolyether alcohol in dissolved and/or dispersed form. By carrying outthe process this way the resulting reaction mixture has not only acompletely different composition but also the amount of glycol used maybe drastically decreased and is, as shown in the examples, in the rangeof 50 to 20% of the amounts necessary during glycolysis according to thestate of the art. By this process a composition of the polyethercomponent results which for the first time allows the production ofelastomeric polyurethanes, foams, elastomers, coatings and sealants fromrecycling polyols without a work-up step. The polyol component with ahigh percentage of long chain polyether alcohols after reaction withpolyisocyanates moves the glass transition temperature of the resultingpolyurethanes to lower values, i.e. at room temperature into the elasticregion, and this value is not moved to markedly higher temperatures bythe low content of low molecular weight diols. By chosing these lowmolecular weight diols according to the invention with respect to typeand amount the upper and lower service temperature of the resultantpolyurethanes may be controlled and predetermined already by thedepolymerization reaction. Based on this the usage of higher molecularweight glycols in the glycol component is prefered in contrast to thestate of the art while the propylene glycols starting with dipropyleneglycol are especially suitable since their secondary hydroxyl groups areless reactive than the usual primary hydroxyl groups of the ethyleneglycol series thus showing nearly the same reactivity as the hydroxylgroups of the long chain polyether alcohols. From these reasons, thepolyols of the present invention show several advantages compared to thestate of the art which are based on their specific properties and lowcost production.

In a further embodiment of the present invention an economicallyfavorable process is the use of technical non-purified amines ordistillation residues from the amine synthesis of aliphatic amines.

The present invention is further illustrated by the following,non-limiting examples.

EXAMPLE 1

In a one liter four-necked flask 100 g diethylene glycol and 40 g ofdi-n-butylamine are heated to 140° C. With continuous stirring 125 gpolyurethane soft foam flakes are introduced within two hours. Thetemperature is raised to 180° C. and kept for 30 minutes. The mixture iscooled and if necessary degassed. The obtained polyol has a hydroxylnumber of 365 mg KOH/g and a viscosity of 3,560 mPas (20° C.). It isused for the production of polyurethane rigid foams and semi-rigidfoams.

EXAMPLE 2

In a one liter four-necked flask 150 g triethylene glycol and 35 g ofdi-n-butylamine are heated to 160° C. With continuous stirring 170 gpolyurethane soft foam flakes are introduced within two and a halfhours. The temperature is raised.to 195° C. and kept there for one hour.The mixture is cooled and if necessary degassed. The obtained polyol hasa hydroxyl number of 326 mg KOH/g and a viscosity of 4,820 mPas (20°C.). It is used for the production of polyurethane rigid foams andsemi-rigid foams.

EXAMPLE 3

In a six liter four-necked flask 600 g diethylene glycol and 250 g ofdi-n-butylamine are heated to 160° C. With continuous stirring 1750 gpolyurethane soft foam flakes are introduced within three hours. Thetemperature is raised to 200° C. and kept there for two hours. Themixture is cooled and if necessary degassed. The obtained polyol has ahydroxyl number of 382 mg KOH/g and a viscosity of 9,500 mPas (200C). Itis used for the production of polyurethane rigid foams and semi-rigidfoams.

EXAMPLE 4

In a six liter four-necked flask 1000 g polyethylene glycol 400 and 64 gof di-n-butylamine are heated to 150° C. With continuous stirring 1250 gpolyurethane soft foam flakes are introduced within two hours. Thetemperature is raised to 190° C. and kept there for three hours. Themixture is cooled and if necessary degassed. The obtained polyol has ahydroxyl number of 326 mg KOH/g and a viscosity of 4,480 mPas (20° C.).It is used for the production of polyurethane rigid foams and semi-rigidfoams.

EXAMPLE 5

In a 2,5 liter four-necked flask 200 g polyethylene glycol 400, 150 g ofdipropylene, glycol and 80 g of di-n-butylamine are heated to 1500C.With continuous stirring 625 g polyurethane soft foam flakes areintroduced within four hours. The temperature is raised to 210° C. andkept there for two hours. The mixture is cooled and if necessarydegassed. The obtained polyol has a hydroxyl number of 288 mg KOH/g anda viscosity of 1,880 mPas (20° C.). It is used for the production ofpolyurethane rigid foams and semi-rigid foams.

EXAMPLE 6

In a one liter four-necked flask 150 g polyethylene glycol 400, 50 gdipropylene glycol, and 70 g of di-n-butylamine are heated to 150° C.With continuous stirring 550 g polyurethane soft foam flakes areintroduced within three hours. The temperature is raised to 200° C. andkept there for two hours. The mixture is cooled and if necessarydegassed. The obtained polyol has a hydroxyl number of 221 mg KOH/g anda viscosity of 5,640 mPas (20° C.). It is used for the production ofpolyurethane rigid foams and semi-rigid foams.

EXAMPLE 7

In a 2,5 liter four-necked flask 290 g dipropylene glycol and 45 g ofdi-n-butylamine are heated to 180° C. With continuous stirring 750 gpolyurethane soft foam flakes are introduced within three hours. Thetemperature is raised to 200° C. and kept there for two hours. Themixture is cooled and if necessary degassed. The obtained polyol has ahydroxyl number of 290 mg KOH/g and a viscosity of 8,500 mPas (20° C.).It is used for the production of polyurethane rigid foams and semi rigidfoams.

EXAMPLE 8

In a 2,5 liter four-necked flask 290 g dipropylene glycol and 53 g ofdi-n-butylamine are heated to 150° C. With continuous stirring 850 gpolyurethane soft foam flakes are introduced within three hours. Thetemperature is raised to 210° C. and kept there for two hours. Themixture is cooled and if necessary degassed. The obtained polyol has ahydroxyl number of 276 mg KOH/g and a viscosity of 4,200 mPas (20° C.).It is used for the production of polyurethane rigid foams and semi-rigidfoams.

What is claimed is:
 1. A process for producing polyols bydepolymerization of polyurethane wastes in the presence of hydroxylgroup containing compounds at elevated temperatures comprising the stepsof: introducing polyurethane wastes into a mixture of at least one dioland at least one secondary alkyl amine, and reacting said polyurethanewastes with said mixture of at least one diol having a molecular weightof 108 to 800 and at least one secondary alkyl amine at temperatures inthe range of 120 to 220° C.; wherein the weight ratio of said at leastone diol to said secondary alkyl amine is between 1:1 to 10:1, and theweight ratio of said mixture of diol and secondary alkyl amine topolyurethane is up to 1:12.
 2. The process according to claim 1 wereinsaid at least one diol is diethylene glycol.
 3. The process according toclaim 1 wherein said at least one diol is triethylene glycol.
 4. Theprocess according to claim 1 wherein said at least one diol istetraethylene glycol.
 5. The process according to claim 1 wherein saidat least one diol is pentaethylene glycol.
 6. The process according toclaim 1 wherein said at least one diol is a mixture of ethylene glycols.7. The process according to claim 1 wherein said at least one diol is apolyethylene glycol having a molecular weight of 180 to 800 or a mixtureof said polyethylene glycols.
 8. The process according to claim 1wherein said at least one diol is an oligopropylene glycol having amolecular weight between 134 and
 800. 9. The process according to claim1 wherein said secondary alkyl amine is a crude amine.
 10. The processaccording to claim 1 wherein said secondary alkyl amine is adistillation residue obtained from the synthesis of aliphatic amines.11. A process for producing polyols by depolymerization of polyurethanewastes in the presence of hydroxyl group containing compounds atelevated temperatures comprising the steps of: gradually reactingpolyurethane soft foams in a mixture of a lower molecular weightpolyalkylene glycol and a secondary alkyl amine at a temperature between120 and 220° C., wherein a weight ratio of polyalkylene glycol tosecondary alkyl amine is between 3:1 to 10:1, and the weight ratio ofthe mixture of polyalkylene glycol to secondary alkyl amine topolyurethane soft foam is up to 1:12.
 12. A process according to claim11, wherein the weight ratio of polyalkylene glycol to secondary alkylamine is between 1:1 to 1:7, and the weight ratio of said mixture ofpolyalkylene glycol and secondary alkyl amine to said polyurethane rigidfoam is up to 1:8.
 13. The process according to claim 11 wherein: saidpolyalkylene glycol is a polyalkylene glycol having a molecular weightbetween 108 to 600, and said secondary alkyl amine is a di-n-alkyl aminehaving an alkyl group chain length of between 2 to 6, and saidtemperature is in the range between 130 to 200° C.
 14. The processaccording to claim 1 wherein said secondary alkyl amine isdi-n-butylamine.
 15. Polyols produced by the process of any one ofclaims 1 to
 14. 16. Polyols produced by the process of depolymerizationof polyurethane wastes in the presence of hydroxyl group containingcompounds at elevated temperatures comprising the steps of: introducingpolyurethane wastes into a mixture of at least one diol and at least onesecondary alkyl amine, and reacting said polyurethane wastes with saidmixture of at least one diol and at least one secondary alkyl amine attemperatures in the range of 120 to 220° C.; wherein the weight ratio ofsaid at least one diol to said secondary alkyl amine is between 1:1 to10:1, and the weight ratio of said mixture of diol and secondary alkylamine to polyurethane is up to 1:12, and wherein said polyols consistessentially of a mixture of high molecular weight, at least twofunctional polyether polyols as derived from the original polyurethane,at least one low molecular weight diol, at least one two functionalpolyalkylene glycol, di-and/or polyureas as reaction products from theoriginal polyurethane, tertiary amines from the original polyurethaneand polyether silicones from the original polyurethane.
 17. Polyolsproduced by the process of depolymerization of polyurethane wastes inthe presence of hydroxyl group containing compounds at elevatedtemperatures comprising the steps of: introducing polyurethane wastesinto a mixture of at least one diol and at least one secondary alkylamine, and reacting said polyurethane wastes with said mixture of atleast one diol and at least one secondary alkyl amine at temperatures inthe range of 120 to 220° C.; wherein the weight ratio of said at leastone diol to said secondary alkyl amine is between 1:1 to 10:1, and theweight ratio of said mixture of diol and secondary alkyl amine topolyurethane is up to 1:12, and wherein said polyols consist of amixture of three functional high molecular weight polyether alcohols ofaverage molecular weight between 2,500 and 10,000 from polyurethanefoams, one or more low molecular weight diols of molecular weightbetween 108 and 800, di-and/or polyureas from the polyurethane foam,tertiary amines and polyether silicones both from the originally usedpolyurethane.
 18. Polyols produced by the process of depolymerization ofpolyurethane wastes in the presence of hydroxyl group containingcompounds at elevated temperatures comprising the steps of: introducingpolyurethane wastes into a mixture of at least one diol and at least onesecondary alkyl amine, and reacting said polyurethane wastes with saidmixture of at least one diol and at least one secondary alkyl amine attemperatures in the range of 120 to 220° C.; wherein the weight ratio ofsaid at least one diol to said secondary alkyl amine is between 1:1 to10:1, and the weight ratio of ksaid mixture of diol and secondary alkylamine to polyurethane is up to 1:12, and wherein said poluols consist ofa mixture of 35 to 60 weight percent nominally three functional highmolecular weight polyether alcohols of average molecular weight between2,500 and 10,000, 10 to 20 weight percent di-and/or polyureas, 0.001 to1 weight percent tertiary amines, 0.1 to 5 weight percent polyethersilicones derived from the original polyurethane, and 5 to 10 weightpercent of one or a mixture of low molecular weight diols.
 19. A processfor producing polyols by depolymerization of polyurethane, wastes in thepresence of hydroxyl group containing compounds at elevated temperaturescomprising the steps of: gradually reacting polyurethane elastomers ormicrocellular elastomers with a mixture of a diol and at least onesecondary alkyl amine at a temperature between 120 and 220° C., whereina weight ratio. of said diol to said secondary alkyl amine is between1:2 to 1:9, and the weight ratio of said mixture of said diol and said.secondary alkyl amine to said polyurethane elastomers or microcellularelastomers is up to 1:9.